Protection of laser bond inspection optical components

ABSTRACT

Methods, systems, and apparatuses are disclosed for the protection of optical components used during laser bond inspection. In one embodiment, an optic surface wetting enhancement is provided on a protective optic to assist in forming a substantially flat film of transparent liquid from transparent liquid applied to a surface of a protective optic. A flat film of transparent liquid on a surface of a protective optic may be used to retain debris and effluent backscatter produced during a laser bond inspection process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/554,011, filed Nov. 25, 2014, entitled “PROTECTION OF LASER BONDINSPECTION OPTICAL COMPONENTS” which claims the benefit of U.S.Provisional Patent Application No. 61/908,192, filed Nov. 25, 2013,entitled “PROTECTION OF LASER BOND INSPECTION OPTICAL COMPONENTS.” Theentire contents of each of the above-identified applications areincorporated herein by reference.

BACKGROUND

Laser bond inspection (LBI) may be used for non-destructive inspectionof structures assembled with adhesive bonds. LBI typically involvesdepositing laser energy onto the front surface of a bonded article,thereby generating compression waves that reflect off of a back surfaceof the bonded article as tensile waves. The tensile waves providestresses that interrogate the strength or relative quality of a bond.

Similar to LBI is laser induced bond delamination, which generallyincludes laser processing a bonded structure to intentionally inducedefects in one or more bonds contained in the bonded structure.

With reference to FIG. 1, a general LBI and bond delamination process100 is illustrated. In each of these applications, before laserprocessing a workpiece, an overlay coating 112, which may besubstantially opaque to laser beam 102, may be applied to a frontsurface 106 of a workpiece being processed. An additional layer 110,which may be substantially transparent to laser beam 102, may be appliedover opaque overlay 112, or directly onto workpiece surface 106 (i.e.,no opaque overlay coating is applied). Opaque overlay 112 may include,without limitation, tape, paint, or a liquid erosion-resistant coatingas described in U.S. Pat. No. 7,268,317, which is incorporated herein byreference in its entirety. Transparent overlay 110 may include, but isnot limited to, water, water-based solution, other noncorrosive liquids,glass, sodium silicate, fused silica, potassium chloride, sodiumchloride, polyethylene, fluoroplastics, nitrocellulose, and mixturesthereof.

Laser pulse 102 passes through transparent overlay 110 and strikesopaque overlay 112, causing a portion of opaque overlay 112 to vaporize.The vapor absorbs the remaining laser energy and produces a rapidlyexpanding plasma plume 118. Since expanding plasma 118 is confinedmomentarily between workpiece surface 106 and transparent overlay 110, arapidly rising high-pressure shock wave 108 is created which propagatesinto material 104. Compressive wave 108 propagates through material 104and may reflect off back surface 116 of material 104 as a tensile wave(not shown) to interrogate bond 114, or may be used to introduce defectsinto bond 114.

An LBI process often produces debris and effluent backscatter fromtarget sources, contaminating nearby optics such as a final focusinglens, and other optical components of LBI equipment. In some instances,these contaminants accumulate on optical components, such as lenses,during LBI, and absorb laser radiation which may cause damage to opticalcomponents. Thus, what is needed is a simple, low-cost solution toprotect laser bond inspection optical components.

SUMMARY

In one embodiment, a protective optic for use in a laser bond inspectionsystem to protect components of the laser bond inspection system fromeffluent backscatter and debris produced during a laser bond inspectionprocess is provided, the protective optic comprising: a first surfaceand a second surface opposite each other, the first surface and thesecond surface comprising a central portion configured to transmit alaser beam from a laser beam delivery system of the laser bondinspection system, the second surface oriented nearer the laser beamdelivery system, the first surface comprising an optic surface wettingenhancement modification such that the first surface is configured tosupport a transparent liquid on the first surface which is effective toretain the effluent backscatter and the debris.

In another embodiment, a laser bond inspection system having aprotective optic with enhanced surface wetting for protecting componentsof the laser bond inspection system from effluent backscatter and debrisduring a laser bond inspection process is provided, the laser bondinspection system comprising: (1) a laser configured to produce a laserbeam; (2) a laser beam delivery system, the laser beam delivery systemconfigured to deliver the laser beam from the laser source to aninspection head, the laser beam delivery system comprising at least oneof: one or more mirrors, one or more optical fibers, and an articulatedarm; (3) an inspection head, the inspection head configured to outputthe laser beam to a workpiece surface, the inspection head comprising: ahousing; a first output to output the laser beam; at least one secondoutput configured to output at least one of: a transparent overlay, anda transparent liquid; a final focusing optic; and one or more evacuationports for removing the transparent liquid; and (4) a protective opticfor protecting components of the laser bond inspection system within theinspection head housing from effluent backscatter and debris during alaser bond inspection process, the protective optic comprising: a firstsurface and a second surface opposite each other, the first surface andthe second surface comprising a central portion configured to transmit alaser beam from a laser beam delivery system, the second surfaceoriented nearer the laser beam delivery system, the first surfacecomprising an optic surface wetting enhancement modification such thatthe first surface is configured to support the transparent liquid on thefirst surface which is effective to retain the effluent backscatter andthe debris.

In another embodiment, a method for laser bond inspection is provided,the method comprising: wetting at least one surface of a protectiveoptic comprising an optic surface wetting enhancement with a transparentliquid; forming a substantially flat film of the transparent liquid;transmitting a laser through at least a transparent portion of theprotective optic and the substantially flat film of the transparentliquid to lase a surface of a workpiece for laser bond inspection;lasing at least one of: a transparent overlay, and an opaque overlay onthe workpiece surface to produce a plasma plume for laser bondinspection; retaining effluent backscatter or debris produced by theplasma plume in the substantially flat film of the transparent liquid;and evacuating at least a portion of the substantially flat film of thetransparent liquid from the at least one surface of the protective optichaving the optic surface wetting enhancement.

In one embodiment, the smooth coverage of a transparent liquid on theprotective optic surface allows for the laser inspection head to be usedin various orientations.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, which are incorporated in and constitute apart of the specification, illustrate various example systems andmethods, and are used merely to illustrate various example embodiments.

FIG. 1 illustrates a schematic of an LBI application.

FIG. 2 illustrates one embodiment of an LBI system.

FIG. 3 illustrates one embodiment of a protective optic used in an LBIsystem.

FIG. 4 illustrates one embodiment of an LBI system using a protectiveoptic.

FIG. 5a illustrates an alternative embodiment of a protective optic usedduring LBI.

FIG. 5b illustrates an alternative embodiment of a protective optic usedduring LBI.

FIG. 6 illustrates an example schematic embodiment of a protective opticwithin a laser inspection head.

FIG. 7 illustrates a flowchart depicting one embodiment of a method forproducing a protective optic used during LBI.

FIG. 8 illustrates a flowchart depicting an alternative embodiment of amethod for producing a protective optic used during LBI.

FIG. 9 illustrates a flowchart depicting one embodiment of a method forLBI using a protective optic.

DETAILED DESCRIPTION

The embodiments claimed herein disclose using a protective optic with alaser bond inspection (LBI) system. With reference to FIG. 2, an LBIsystem 200 for laser bond inspection is provided. In one embodiment, LBIsystem 200 may be used for LBI of a bonded article 210. System 200comprises: a laser 220; a laser beam delivery system 230; and aninspection head 240.

In one embodiment, laser 220 may comprise, for example, a neodymiumglass laser, such as, for example, those manufactured by LSPTechnologies, Inc., a YAG laser, a YLF laser, or any other solid-statecrystal material, in either a rod or a slab gain medium. Laser 220 maybe configured to deliver laser pulses 102 having a pulse energy ofbetween about 3 J and about 50 J (at the output of the final amplifiermodule), a wavelength of about 1 μm, and a pulse width of between about70 ns and 300 ns, and further being configured to deliver the laserpulses 102 in a low-high-low or probe-pump-probe pulse energy sequence(i.e., a first laser pulse 102 having a first energy, a second laserpulse 102 having a second energy that is greater than the first energybut less than an energy required to break a properly constructed or“good” bond, and a third laser pulse 102 having an energy which isapproximately the same as the first pulses' energy), as described andillustrated in U.S. Pat. Nos. 7,770,454 and 8,156,811. Beam diameter forLBI is selected as a compromise between the need to have a large areafor planar wave generation and a reasonable sized beam for theinspection of small zones in the object. A beam size of about 10.0 mm isa suitable compromise. The use of a large diameter laser beam of severalmm or more generates suitable internal stress for the evaluation ofinternal bonds and avoids surface spallation of a bonded article underLBI. Fluence is a measure of energy delivered per unit area, and LBIuses fluence values ranging between about 4 J/cm² to about 6 J/cm² forinterrogation of weak bonds, while medium strength bonds fail aroundabout 16 J/cm². Further configurations of laser 220 may include thosedescribed and illustrated in U.S. Pat. Nos. 7,770,454 and 8,156,811.

In one embodiment, laser beam delivery system 230 may comprise, forexample, at least one of: (a) one or more mirrors; (b) an articulatedarm; and (c) one or more fiber optics (also referred to herein asoptical fibers), and includes a laser beam delivery systems describedand illustrated in U.S. Pat. Nos. 7,770,454 and 8,156,811. In oneembodiment, where laser beam delivery system 230 is one or more mirrors,the beam 102 may be directed to the surface 106 of bonded article 210.In alternative embodiments, where laser beam delivery system 230 is anarticulated arm and/or a fiber optic, laser beam delivery system 230 maybe operatively connected to inspection head 240.

With reference to FIG. 3, an example protective optic 300 for use in,e.g., inspection head 240 of LBI system 200 is illustrated. Protectiveoptic 300 may comprise a substantially transparent region 302 surroundedby a frosted region 304 around the perimeter of protective optic 300. Inone embodiment, protective optic 300 may be a lens or window of amaterial configured to transmit light such as glass, transparentpolymeric material, and the like. Frosted region 304 appears “frosted”due to the intentional introduction of multiple defects and multipleimpurities on one or more surfaces of protective optic 300. Such defectsand impurities may be pits or pores created in a surface of protectiveoptic 300. A high density of pits and pores on a surface creates a roughsurface on protective optic 300 giving a “frosted” appearance. Multipledefects and impurities may be formed on protective optic 300 bymechanical abrasion processes, chemical etching, and the like. In oneembodiment, frosted region 304 is formed by a mechanical abrasionprocess such as grit blasting or sandblasting where an abrasive mediasuch as aluminum oxide is mixed with a high pressure gas stream toabrade a surface of protective optic 300 causing surface deformation. Inanother embodiment, frosted region 304 is formed by a chemical etchingprocess where an acidic or caustic chemical etchant, such as sodiumfluoride or hydrogen fluoride containing compounds, is applied toprotective optic 300. Etching chemicals react with material ofprotective optic 300 to deform a surface of protective optic 300.

One or more surfaces of protective optic 300 may be coated with ananti-reflective (AR) coating to substantially reduce reflection of abeam 102 produced by laser 220 on protective optic 300 which could causeunwanted feedback in laser 220. In one embodiment, a normal AR coatingis used on protective optic surface 300. In another embodiment, ahydrophilic AR coating is used on a surface of protective optic 300.Target side surface 301 a of protective optic 300 may not require an ARcoating, as a transparent liquid applied to target side surface 300 amay substantially reduce reflections at the liquid/protective optic 300interface.

In one embodiment, frosted region 304 may be in the form of an annulusor annular ring on an outer perimeter of a circular shaped protectiveoptic 300. However, frosted region 304 and protective optic 300 are notlimited to a circular shape. Additionally, frosted region 304 is notlimited to being formed on an outer perimeter of protective optic 300.Frosted region 304 may be formed on a substantial portion or an entireoptical surface of protective optic 300. The inside diameter d offrosted region 304 may be varied to optimize a formation of a nearlyoptically flat, wetted surface of a liquid applied on a target sidesurface of protective optic 300 which is a surface closest to a targetsurface, e.g., 106. While not bound to any particular theory, an elementfor establishing and maintaining a nearly optically flat liquid film isa surface tension of the liquid. Water, as an example liquid, has astrong surface tension and due to strong cohesive forces between watermolecules will naturally try to form into a sphere when there are nooutside forces acting upon it. On a nonpolar surface such as opticalglass (e.g. protective optic 300), water droplets will naturally try toform into spherical droplets while the force of gravity acts to slightlyflatten the spherical droplets making them less spherical. Due to lowadhesion forces between the water droplets and the nonpolar surface, thenatural tendency of water and its strong cohesive force between watermolecules is to minimize its contact with such a surface such that waterwill separate into spherical drops or beads instead of uniformly wettingthe surface in a nearly optically flat, thin film (i.e. substantiallyflat). In a surface with a high density of surface defects (e.g. frostedregion 304), the pores and pits of this region act as capillaries,sourcing water from the surrounding regions (e.g. substantiallytransparent region 302) toward frosted region 304 by a capillary action.Frosted region 304 also increases adhesion forces of the surface suchthat the cohesive forces between the water molecules are weakened, andthe increased adhesion of frosted area 304 prevents water fromsubstantially transparent region 302 from flowing away, allowing a thinfilm of water to remain in place during an LBI process, and forming asubstantially flat, thin film on a target-side surface of protectiveoptic 300.

With reference to FIG. 4, one embodiment 400 of LBI system 200 usingprotective optic 300 is illustrated. In one embodiment, a laser beam 102from laser 220 delivered via laser beam delivery system 230 passesthrough a final focusing optic 442 and protective optic 300 ininspection head 240 before contacting target surface 106 of bondedarticle 210. Final focusing optic 442 and protective optic 300 may becombined into one optic such that substantially transparent region 302and frosted region 304 are incorporated onto a surface final focusingoptic 442 in addition to other optical properties of final focusingoptic 442.

Inspection head 240 may additionally include one or more liquid deliverymechanisms 444. Generally, one or more liquid delivery mechanisms 444,applicator tubes 448, and nozzles 448 may be referred to hereincollectively as an “output,” or “liquid output,” for example, to outputa transparent liquid. Liquid delivery mechanisms 444 may be configuredon inspection head 240 to provide either of a liquid transparent overlay110 or transparent liquid 454. Each of one or more liquid deliverymechanisms 444 may be adapted to perform a specified function. Forexample, one liquid delivery mechanism 444 may be configured to deliveronly a liquid transparent overlay 110 to a surface of a workpiece, whileanother liquid delivery mechanism 444 may be adapted to provide only atransparent liquid 454 to a surface 301 a of protective optic 300. Inone embodiment, liquid delivery mechanism 444 may be a pump used tosupply a liquid such as water via a liquid applicator tube 446 for useas transparent liquid 454. In the illustrated embodiment, a transparentliquid 454 may be applied to target surface side 301 a of protectiveoptic 300 by liquid delivery mechanism 444 through liquid applicatortube 446. Liquid applicator tube 446 may be a rigid tube or a flexibletube. Liquid applicator tube 446 may be constructed of metal, glass, ora polymeric material. Liquid applicator tube 446 (and any “applicatortube” described in the present embodiments) may alternatively be anytype of apparatus know in the art that is capable of transferring orallowing a flow of liquid from liquid delivery mechanism 444 to asurface of the optic (e.g., a machine channel). In one embodiment,liquid applicator tube 446 has a nozzle 448 on one end to control adirection or characteristics of fluid flow of liquid in liquidapplicator tube 446. In one embodiment, nozzle 448 directs and controlsfluid flow of transparent liquid 454 from liquid delivery mechanism 444and outputs transparent liquid 454 near a perimeter of protective optic300. In another embodiment, liquid delivery mechanism 444 may have oneliquid applicator tube 446 positioned near a perimeter of protectiveoptic 300, and one liquid applicator tube 446 positioned near a centerof protective optic 400 to provide a transparent liquid 454 to targetside surface 301 a of protective optic 300.

Transparent liquid 454 may be water or any other liquid that is notharmful to protective optic 300 and is substantially transparent tolaser beam 102. In one embodiment, transparent liquid 454 contains asurfactant that reduces surface tension to encourage formation of a flatliquid film on target side surface 301 a when transparent liquid 454 isapplied to protective optic 300.

In various embodiments, one or more optic surfaces of protective optic300 may be contacted with one or transparent liquids 454. The one ormore transparent liquids 454 may be configured to protect one or moreoptic surfaces of protective optic 300. The one or more transparentliquids 454 may include a solvent, such as water or an organic solvent.The one or more transparent liquids 454 may be configured to wet the oneor more optic surfaces. For example, the one or more transparent liquids454 may be selected for a hydrophobic or hydrophilic character in accordwith a corresponding hydrophobic or hydrophilic character of the one ormore optic surfaces (i.e. 301 a) to provide a wetting action—that is,liquid selection may be based on optic surface characteristics. The oneor more transparent liquids 454 may be selected for hydrophobic ofhydrophilic character based on the solvent selected—that is, liquidselection may be based on solvent selection. The wetting action of oneor more transparent liquids 454 may also be modified by including awetting agent, such as a surfactant.

Inspection head 240 may additionally include one or more evacuationmechanisms 450. In one embodiment, evacuation mechanism 450 is a vacuumpump. Evacuation mechanism 450 may be capable of removing and exhaustingsolid particles, liquids, gases, or any combination thereof which mayspecifically include: transparent liquid 454 from target side surface301 a of protective optic 300, a liquid transparent overlay 110 appliedto target surface 106 of bonded article 210, gas produced during LBI,effluent backscatter, and debris produced during LBI. Evacuationmechanism 450 includes an evacuation tube 452. In one embodiment,evacuation tube 452 may be located between protective optic 300 andtarget surface 106 of bonded article 210. Evacuation tube 452 mayinclude hardware such as a nozzle or port to direct or modify vacuumflow or vacuum direction. As referred to herein, an “evacuation port”may include evacuation mechanism 450 and evacuation tube 452, and beconfigured to remove material via suction or vacuum.

In one embodiment 400, LBI system 200 with protective optic 300 may beused for LBI of bonded article 210. Prior to laser beam 102 beingapplied to surface 106 of bonded article 210, liquid delivery mechanism444 provides a transparent liquid 454 via liquid applicator tube 446 totarget side surface 301 a of protective optic 300. A control system (notshown) of LBI system 200 may automatically facilitate a process ofwetting protective optic 300, or a wetting process may be initiatedmanually by a button push or similar device. After target side surface301 a of protective optic 300 is wetted with transparent liquid 454, andtransparent liquid 454 is formed into a nearly optically flat, thin filmof transparent liquid 454, liquid application mechanism 444 may beturned off to stop a flow of transparent liquid 454 from liquidapplication mechanism 444 to protective optic 300. Laser 220 may producea laser beam 102 delivered via laser beam delivery system 230 toinspection head 240. Inspection head 240 may include and output whichmay be configured to output laser beam 102 from inspection head 240towards a workpiece surface 106. Inside inspection head 240, laser beam102 passes through a final focusing optic 442, protective optic 300, andtransparent liquid 454 before contacting surface 106 of bonded article210. A high pressure shockwave 108 and plasma plume 118 generated by avaporization of opaque layer 112 may generate debris and effluentbackscatter. Debris may include portions of vaporized opaque layer 112and surface 106. Effluent backscatter may include scattered portions oftransparent liquid overlay layer 110 caused by the shockwave 108 andplasma plume 118 created during an LBI process. Transparent liquid 454prevents accumulation of debris and effluent backscatter on protectiveoptic 300. Debris and effluent backscatter may accumulate in, and beretained within transparent liquid 454. Transparent liquid 454 alongwith protective optic 300 prevents accumulation of debris and effluentbackscatter on final focusing optic 442 and other optical components ininspection head 240. After an LBI process concludes, transparent liquid454 may be removed from protective optic 300 via a vacuum stream inevacuation tube 452 produced by evacuation mechanism 450—that is,transparent liquid 454 retaining debris and effluent backscatter may beevacuated through an evacuation port after an LBI process. In oneembodiment, transparent liquid 454 remains in place on protective optic300 during LBI for an entire LBI operation. In another embodiment,transparent liquid 454 is removed by evacuation mechanism 450 after anLBI process for each target area. In one embodiment, evacuation oftransparent liquid 454 by evacuation mechanism 450 may be initiatedautomatically by a control system (not shown) of LBI system 200. Inanother embodiment, evacuation of transparent liquid 454 may beinitiated manually by a button push or similar device.

With reference to FIGS. 5a and 5b , an alternative embodiment ofprotective optic 500 for use in, e.g., inspection head 240 of LBI system200 is provided. Protective optic 500 may comprise a substantiallytransparent aperture region 502 surrounded by a wicking material region504 around a perimeter of protective optic 500. Protective optic 500 maybe of a material configured to transmit light such as glass, transparentpolymeric material, and the like. Wicking material region 504 maycontain a material whose properties encourage a capillary action oftransparent liquid 454 over a surface of protective optic 500, such thatwhen a transparent liquid 454 contacts wicking material region 504,transparent liquid 454 in substantially transparent aperture region 502is drawn towards wicking material region 504. Wicking device region 504may be substantially rougher than transparent region 502. In addition,porous material characteristics of wicking material region 504 mayreadily attract, and absorbs water. Wicking material region 504 may beof a material such as, but not limited to: a cloth material, cotton,steel wool, wire mesh, carbon fiber mesh, and the like, or include arough surface. In one embodiment, wicking device region 504 may beformed by securing material to protective optic 500 by an adhesive orthe like. In another embodiment, wicking device region 504 may beintegrated in protective optic 500 through a manufacturing process,whereby wicking device region 504 may be embedded in protective optic500 during the manufacturing process.

One or more surfaces of protective optic 500 may be coated with ananti-reflective (AR) coating to prevent reflection of a beam 102produced by laser 220 on protective optic 500 which could cause unwantedfeedback in laser 220. In one embodiment, a normal AR coating may beused on surfaces of protective optic 500. In another embodiment, ahydrophilic AR coating is used on a surface of protective optic 500.

In one embodiment, wicking material region 504 is in the form of anannulus or annular ring on an outer perimeter of a circular shapedprotective optic 500 as in FIG. 5a . However, wicking material region504 and protective optic 500 are not limited to a circular shape.

FIG. 5b illustrates a different embodiment with a parallel railconfiguration of wicking material region 504. In this embodiment,wicking material region 504 comprises two wicking material strips 504 aand 504 b which are separated by substantially transparent aperture 502.Transparent liquid 454 is drawn toward wicking material strips 504 a and504 b such that a nearly optically flat, thin film of transparent liquid454 covers substantially transparent aperture 502.

As used herein, an optic surface wetting enhancement modification mayinclude any and all of the aforementioned embodiments used to form of asubstantially flat film of transparent liquid 454 on one or moresurfaces of protective optic 300. A surface wetting enhancementmodification may include, but is not limited to: a plurality of surfacedeformations, a wicking material, a hydrophilic coating, and a wettingagent or surfactant added to transparent liquid 454.

With reference to FIG. 6, a schematic view of one embodiment of laserinspection head 240 that facilitates delivery of laser beam 102 fromarticulated arm of laser beam delivery system 230 to a bonded structuresurface 106 is illustrated. Laser inspection head 240 includes a housing656. Final focusing optic 442 protected by protective optic 300 isdisposed within housing 656. Further, liquid applicator tube 446, liquidapplicator mechanism 444, evacuation tube 452, and evacuation mechanism(not shown) are also disposed within housing 656.

With reference to FIG. 7, a flowchart depicting one embodiment of amethod 700 for producing a protective optic for use in an LBI system isprovided. In step (701), a liquid exposed protective optic surface istreated with a first AR coating. The liquid exposed protective opticsurface is the target side surface 301 a of protective optic 300. Instep (703), an air exposed protective optic surface—that is a surfacenearer to LBI components in inspection head 240—is treated with a secondAR coating. Because of a difference in the index of refraction betweenair and liquids, first AR coating will be optimized to minimizereflections at liquid exposed protective surface depending on thetransparent liquid 454 used in system 400, while second AR coating willbe optimized to minimize reflections at air exposed protective surface.A custom AR coating with hydrophilic properties may be employed on oneor both liquid exposed protective surface, and air exposed protectivesurface to increase a sheeting effect of transparent liquid 454 toproduce a nearly optically flat, thin film of transparent liquid 454. Instep (705), a perimeter portion of at least liquid exposed protectiveoptic surface is abraded with an abrasive media through a high pressuregas stream to deform liquid exposed protective surface such that a highdensity of pits and pores are produced in liquid exposed protectiveoptic surface to produce a substantially rough surface with a frostedappearance.

With reference to FIG. 8, a flowchart depicting another embodiment of amethod 800 for producing a protective optic for use in an LBI system isprovided. In step (801), a liquid exposed protective optic surface istreated with a first AR coating. The liquid exposed protective opticsurface is the target side surface 301 a of protective optic 300. Instep (803), an air exposed protective optic surface is treated with asecond AR coating. Because of a difference in the index of refractionbetween air and liquids, first AR coating will be optimized to minimizereflections at liquid exposed protective surface depending on thetransparent liquid 454 used in system 400, while second AR coating willbe optimized to minimize reflections at air exposed protective surface.A custom AR coating with hydrophilic properties may be employed on oneor both liquid exposed protective surface and air exposed protectivesurface to increase a sheeting effect of transparent liquid 454 toproduce a nearly optically flat, thin film of transparent liquid 454. Instep (805), a perimeter portion of at least liquid exposed protectiveoptic surface is etched with a chemical etchant to deform liquid exposedprotective surface such that a high density of pits and pores areproduced in liquid exposed protective optic surface to produce asubstantially rough surface with a frosted appearance.

With reference to FIG. 9, a flowchart illustrating an example method 900for LBI using a protective optic is provided. In step (901), at leastone surface (i.e. surface 301 a) of protective optic 300 with an opticsurface wetting enhancement is wetted with transparent liquid 454. Instep (903), an optic surface wetting enhancement causes transparentliquid 454 to form into a substantially flat film of transparent liquid454. In step (905), a laser beam 102 is transmitted throughsubstantially transparent region 302 of protective optic 300 andsubstantially flat film of transparent liquid 454 to a workpiece surface106. In step (907), laser beam 102 lases at least one of: an opaqueoverlay 112, and a transparent overlay 110 to produce plasma plume 118.In step (909) debris and effluent backscatter produced by plasma plume118 may interacts with, and may be retained within substantially flatfilm of transparent liquid 454. In step (911), all or portion ofsubstantially flat film of transparent liquid 454 covering protectiveoptic 300 and debris and effluent backscatter contained therein isevacuated.

Unless specifically stated to the contrary, the numerical parameters setforth in the specification, including the attached claims, areapproximations that may vary depending on the desired properties soughtto be obtained according to the exemplary embodiments. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Furthermore, while the systems, methods, and apparatuses have beenillustrated by describing example embodiments, and while the exampleembodiments have been described and illustrated in considerable detail,it is not the intention of the applicants to restrict, or in any waylimit, the scope of the appended claims to such detail. It is, ofcourse, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the systems,methods, and apparatuses. With the benefit of this application,additional advantages and modifications will readily appear to thoseskilled in the art. Therefore, the invention, in its broader aspects, isnot limited to the specific details and illustrative example andexemplary embodiments shown and described. Accordingly, departures maybe made from such details without departing from the spirit or scope ofthe general inventive concept. Thus, this application is intended toembrace alterations, modifications, and variations that fall within thescope of the appended claims. The preceding description is not meant tolimit the scope of the invention. Rather, the scope of the invention isto be determined by the appended claims and their equivalents.

As used in the specification and the claims, the singular forms “a,”“an,” and “the” include the plural. To the extent that the term“includes” or “including” is employed in the detailed description or theclaims, it is intended to be inclusive in a manner similar to the term“comprising,” as that term is interpreted when employed as atransitional word in a claim. Furthermore, to the extent that the term“or” is employed in the claims (e.g., A or B) it is intended to mean “Aor B or both.” When the applicants intend to indicate “only A or B, butnot both,” then the term “only A or B but not both” will be employed.Similarly, when the applicants intend to indicate “one and only one” ofA, B, or C, the applicants will employ the phrase “one and only one.”Thus, use of the term “or” herein is the inclusive, and not theexclusive use. See Bryan A. Garner, A Dictionary of Modern Legal Usage624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into”are used in the specification or the claims, it is intended toadditionally mean “on” or “onto.” To the extent that the term“selectively” is used in the specification or the claims, it is intendedto refer to a condition of a component wherein a user of the apparatusmay activate or deactivate the feature or function of the component asis necessary or desired in use of the apparatus. To the extent that theterm “operatively connected” is used in the specification or the claims,it is intended to mean that the identified components are connected in away to perform a designated function. Finally, where the term “about” isused in conjunction with a number, it is intended to include ±10% of thenumber. In other words, “about 10” may mean from 9 to 11.

What is claimed is:
 1. An optic comprising: a first surface and a secondsurface opposite each other, the first surface and the second surfaceeach having a transparent central portion configured to pass a laserbeam; a wicking material to support a transparent liquid within thetransparent central portion on the first surface, wherein the wickingmaterial is one of secured to the first surface of the optic by anadhesive and integrated into the optic, wherein the wicking material atthe first surface is located outside the transparent central portion ofthe first surface at a periphery of the transparent central portion ofthe first surface; and wherein the wicking material is configured todraw the transparent liquid from the transparent central portion of thefirst surface toward the periphery of the first surface and cause thetransparent liquid to form in a substantially flat film on thetransparent central portion.
 2. The optic of claim 1, wherein one of thefirst surface, the second surface and both is coated with ananti-reflective (AR) coating.
 3. The optic of claim 1, wherein one ofthe first surface and the second surface is coated with a hydrophilicanti-reflective (AR) coating.
 4. The optic of claim 1, wherein thewicking material is one of a cloth material, cotton, steel wool, a wiremesh and a carbon fiber mesh.
 5. The optic of claim 1, wherein thewicking material is in a form of one of an annulus and an annulus ring.6. The optic of claim 1, wherein the wicking material has a non-circularshape.
 7. An optic comprising: a first surface and a second surfaceopposite each other, the first surface and the second surface eachhaving a transparent central portion configured to pass a laser beam;and a wicking material to support a transparent liquid within thetransparent central portion on the first surface, wherein the wickingmaterial is one of secured to the first surface of the optic by anadhesive and integrated into the optic, wherein the wicking material atthe first surface is located outside the transparent central portion ofthe first surface.
 8. The optic of claim 7, wherein the wicking materialis configured to draw the transparent liquid from the transparentcentral portion of the first surface.
 9. The optic of claim 8, whereinthe drawing of the transparent liquid causes the transparent liquid toform in a flat film on the transparent central portion.
 10. The optic ofclaim 7, wherein the wicking material is located at a periphery of thetransparent central portion of the first surface.
 11. The optic of claim7, wherein one of the first surface, the second surface and both iscoated with an anti-reflective (AR) coating.
 12. The optic of claim 7,wherein one of the first surface and the second surface is coated with ahydrophilic anti-reflective (AR) coating.
 13. The optic of claim 7,wherein the wicking material is one of a cloth material, cotton, steelwool, a wire mesh and a carbon fiber mesh.
 14. The optic of claim 7,wherein the wicking material is in a form of one of an annulus, anannulus ring and a non-circular shape.
 15. A method for forming an opticcomprising: treating a first surface of an optic with a firstant-reflective (AR) coating having a first index of refraction; treatinga second surface of the optic with a second type of AR coating have asecond index of refraction, wherein the first and the second surfaceeach have a transparent central portion; and deforming a perimetersurface portion of the second surface to produce a roughened surface ata periphery of the transparent central portion of the first surface tosupport a transparent liquid within the transparent central portion,wherein the roughened surface is configured to draw the transparentliquid from the transparent central portion of the first surface towardthe periphery and cause the transparent liquid to form in asubstantially flat film on the transparent central portion.
 16. Themethod of claim 15, wherein the roughened surface at the periphery ofthe transparent central portion of the first surface supports thetransparent liquid within the transparent central portion during a laserbond inspection process.
 17. The method of claim 15, wherein one of thefirst AR coating, the second AR coating and both comprise hydrophilicproperties to increase a sheeting effect of the transparent liquid. 18.The method of claim 15, wherein the deforming comprises abrading with anabrasive media through a high pressure gas stream the perimeter surfaceportion to produce pits and pores at the perimeter surface portion ofthe second surface.
 19. The method of claim 15, wherein the deformingcomprises etching with a chemical etchant the perimeter surface portionof the second surface to produce pits and pores at the perimeter surfaceportion of the second surface.
 20. The method of claim 15, wherein thetransparent liquid comprises one of water and an organic solvent.